What should I do in case I want change SSH RSA public key which I used
in deploying?
Sorry, I have not find how to change the public key of VMSS, I will do some search, if I get anything new, I'll keep you updated.
As a workaround, we can add a new public key to VMSS, here is the script:
$vmssName = "dcos-agent-private-EAF6BCA8-vmss0"
$vmssResourceGroup = "dcos"
$vmss = Get-AzureRmVmss -ResourceGroupName $vmssResourceGroup -VMScaleSetName $vmssName
Add-AzureRmVmssSshPublicKey -VirtualMachineScaleSet $VMSS -KeyData "ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAr1ftAx4QhtzAeqei9ukw32nrM8kmB6t2UVdBpuUjAeBAI3/cln/0vmekCt2OPJof5/mdaMTYoMleMsPxQWcm19fZviiMS0rkmLU9qwTeJf8+T8RWEUB75wRH5aDdrit1eYZ9bwJGL1LbkECKWoB02HZGLRH24Z5BLLXCkXjGI8LTLTTZobAnM4EC1QGMCsuMUl0mlhchaK0yQifx+GHOsbFuqe+E40akAzzh7tt+O4I/TjigrE4YHUJlmGNlY3grXFPE5oaszzb97/yyglt1cW2KucjAI4qm7ZTQ6wz5asW8IoN+jya4h2O4Au0ymNVgw1EQG1p8UJ2qByyxxJNMSw==" -Path "/home/admin/.ssh/authorized_keys"
Here is the result:

By the way, if you don't want user can use your original public key to login VMSS instance, we can login this instance and delete the original public key in authorized_key
.
jason@dcos-agent-public-EAF6BCA8000001:~$ cd .ssh/
jason@dcos-agent-public-EAF6BCA8000001:~/.ssh$ ls
authorized_keys
jason@dcos-agent-public-EAF6BCA8000001:~/.ssh$ cat authorized_keys
ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAr1ftAx4QhtzAeqei9ukw32nrM8kmB6t2UVdBpuUjAeBAI3/cln/0vmekCt2OPJof5/mdaMTYoMleMsPxQWcm19fZviiMS0rkmLU9qwTeJf8+T8RWEUB75wRH5aDdrit1eYZ9bwJGL1LbkECKWoB02HZGLRH24Z5BLLXCkXjGI8LTLTTZobAnM4EC1QGMCsuMUl0mlhchaK0yQifx+GHOsbFuqe+E40akAzzh7tt+O4I/TjigrE4YHUJlmGNlY3grXFPE5oaszzb97/yyglt1cW2KucjAI4qm7ZTQ6wz5asW8IoN+jya4h2O4Au0ymNVgw1EQG1p8UJ2qByyxxJNMSw==
Update:
we can use this command to list public key.
